Document and Entity Information
9 Months Ended
Sep. 30, 2018
Document and Entity Information  
Entity Registrant Name MAGELLAN HEALTH INC
Entity Central Index Key 0000019411
Document Type 10-Q
Document Period End Date Sep. 30, 2018
Amendment Flag false
Current Fiscal Year End Date --12-31
Entity Current Reporting Status Yes
Entity Filer Category Large Accelerated Filer
Entity Small Business false
Entity Emerging Growth Company false
Entity Common Stock, Shares Outstanding 24,255,074
Document Fiscal Year Focus 2018
Document Fiscal Period Focus Q3